When the rule of Rehoboam was established and he was strong, he abandoned the law of the LORD, and all Israel with him.
Israel was very much disgraced and weakened by being divided into two kingdoms; yet the kingdom of Judah, having both the temple and the royal city, both the house of David and the house of Aaron, might have done very well if they had continued in the way of their duty; but here we have all out of order there. I.
Commenting on 2 Chronicles 12:1-12
And it came to pass, when Rehoboam had established the kingdom,.... Or when the kingdom of Rehoboam was established; the tribes of Judah and Benjamin being firmly attached to him, and great numbers from the other tribes coming over to him, and things going on peaceably and prosperously during the three years that he and his people abode by the pure worship of God: and...
And it came to pass, when Rehoboam had established the kingdom, and had strengthened himself, he forsook the law of the LORD, and all Israel with him. (a) For such is the inconstancy of the people, that for the most part they follow the vices of their governors.